Crystallization and solution of the structure of Isocitrate Dehydrogenase (IDH) complexed with its dedicated Kinase/Phosphatase (IDH D/P) is multifaceted. When solved, the IDH*IDH D/P structure will be the first enzyme kinase structure to be solved to date. Since the crystal structure of IDH D/P has not yet been solved, solution of the complex structure will also yield the first crystal structure of a member of the bifunctional kinase/phosphatase family. Finally, as IDH K/P recognizes and binds to a topological surface of IDH, this system can be used as a model molecular recognition system.